There is a lot of misinformation surrounding round bottom soda bottles. No, the shape was not invented so the bottle had to lay on its side to prevent the cork from drying out. And, while many bottles were transported by ship, bottles were not created in a particular shape like this just for the sake of being used as ballast.
What is true is that the round bottom is an engineering solution to allow greater pressure inside the bottle. Early attempts at carbonation yielded irregular pressure and stronger bottles were needed. A round bottom is stronger than a flat base.
This is a mid to later 19th century bottle and it is a common thing. Put some embossing on it and perhaps give the glass a different color and you have something much less common.
Collectors call this color aqua, although aquas cover a wide range from green to blue tones.
